Fix jsdoc
Restore ol.interaction.Select options
Remove stray option in modify-features example
Scale the text offset by the device's pixel ratio

Fixes #1918
Fix initial state of the Modify interaction

Features that are in the features collection need to be added to the R-Tree.
Create the R-Tree in the Modify constructor

In this way features can be added/removed to/from the R-Tree even when the interaction does not have a map.
Make the Modify interaction more robust

This prevents a JavaScript error when features are added while the interaction does not have a map.
Update node packages

 * closure-util - Driving the compiler, not watching spurious files
 * async - Bugfixes not related to our use, but this may sidestep the Travis errors we're seeing
Correct documentation for `keyboardEventTarget`.
Share editing default styles
Select interaction options are now optional
Mention the workshop in the readme
Put reference to workshop in QuickStart
Initialize snappedToVertex_